Explain why ice floats over water.

Explanation

In ice, the water molecules are tetrahedrally arranged in which each oxygen atom is linked to four H-atoms (two by covalent bonds and other two by H-bonds). This results "open cage" structure of ice. This structure has vacant space among water molecules. It increases the volume of given mass of ice and thus, decreases their density.

In water, hydrogen bonds partially breaks and it fills the vacant space among the water molecules. Hence, their volume decreases and density increases in the liquid form. Therefore, ice floats over water.